Method for removal of oil from wells



United States Patent No Drawing. Filed June 30, 1960, Ser. No. 3,832 16 Ciaims. (Cl. 166-44) The present invention relates to a method for removing oil from wells. More particularly, it is concerned with the problems involved when oil is present in a well during gas drilling, coring of low-pressure formations, well completions, work-over operations, and the like. In solving these problems we employ a class of silicon compounds as oil foaming agents. The discovery of this property, i.e., the ability of silicon compounds to foam petroleum, is considered indeed surprising inasmuch as the prior art has previously regarded these materials to serve as anti-foam agents, particularly in non-aqueous systems.

One of the principal problems in drilling a well using a gas as the circulating fluid is concerned with controlling the flow of formation liquids into the well. Due to the low bottom hole pressures that accompany gas drilling, Water-bearing zones can produce into the well bore after the zone is penetrated by the drill. If a small quantity of water is produced, the wet shale cuttings, when agitated, become sticky and tend to adhere to one another, forming balls which, due to their size, are diflicult to remove from the bottom of the hole. Wet shale also sticks to the formation wall, casing, or drill pipe, forming mud rings which build up during circulation. Both of these conditions can develop to a degree where cuttings and gas are impeded in their passage upward in the annulus. As a result, lost circulation, low penetration rate of the bit and stuck dn'll pipe can result. Entry of a small quantity of water into the well bore may be detected by a decrease or discontinuance of dust or an increase in the humidity of the exhaust gas.

This water is generally most effectively removed by the use of a suitable foaming agent and in this way impairment of the efliciency of the air drilling operation is prevented. Although the entry of formation liquids, consisting primarily of oil, into the well during air drilling operations does not occur too frequently-at least in amounts suflicient to cause difliculty with the drilling operation--serious disadvantages can arise resulting from the entry of oil into the well owing to the fact that the oil does not foam readily and, hence, cuttings cannot be removed easily. Of course, increased gas circulating pressures may be used up to a certain point, but eventually the hydrostatic head of the oil in the well becomes so great that either available compressor capacity cannot handle the problem or it is uneconomical to employ the compressor capacity required to do the job.

In the case of coring operations in low-pressure formations, well work-over jobs, well completion operations, etc., the well is usually full of oil. Normally, this condition requires a time-consuming and expensive swabbing operation to clean out the well before any of the abovementioned procedures can be carried out.

Removal of oil from a well by bringing it up in the form of a foam has previously been recognized as a desirable procedure. However, such art merely suggested, in efiect, an invitation to experiment. Materials such as various water-soluble gums, starch, commercial soaps, etc., have been proposed as agents for foaming oil out of wells, but in our work we have found them .to be far from satisfactory, as the results hereinafter reported show.

Accordingly, it is an object of our invention to provide an inexpensive and efiicient means for recovering oil standing in a well. It is a further object of our invention to provide a method for removing predominantly oil-containing formation liquids as they enter the well by foaming such liquids out of the well It is a still further object to effect such oil removal operations by the use of a class of substantially non-polar compounds that have previously been used as foam breakers, particularly for non-aqueous systems.

We have now discovered, after screening some 2000 compounds, a class of materials capable of accomplishing the above-mentioned objects. These oil foaming agents belong to a class of silicon derivatives known as silicones, and have the following general structural formula:

wherein X represents methyl, aryl and CH3 CH3 C 3 20-70 CH3 the a,w-dichlorophenyl dimethyl siloxanes, such as and a,w-diethylphenyl dirnethyl siloxanes such as C C 3 20-70 C z A number of methods are available for making these compounds, some of which are described in Chemistry of the Silicones, 2nd ed., by E. G. Rochow, published by John Wiley and Sons, Inc., pp. 78 to 82.

I. I 3 Silicones of the above-mentioned type find use in a number of processes in which it is desired to remove petroleum either from a surface or from a cavity such as .4 Billy V. Randall and now abandoned. Briefly, this equipment consisted of a Lucite column 10 feet high, 2. /2 inches I.D., and having concentrically placed therein a a well. The concentration of silicones used to obtain stainless steel tube about inch O.-D. This tube is the desired results will be found to vary with a number 5 preferably cut to stand approximately inch from the. of factors. Thus, the particular application under conbottom of the Lucite column. The column is preferably sideration, the viscosity of the silicone, the amount of oil graduated, and has a removable plug at the bottom for to be removed, and the manner in which the silicone is cleaning purposes and a plug at the top through which applied or introduced are all factors to be evaluated. fluids enter. At a point near the top of the column, there Generally speaking, however, we usually prefer to use is a foam discharge pipe. Gas in measured quantities is these compounds in concentrations of from 0.02 to about introduced into the stainless steel tube. When tests are 5.0 weight percent based on the oil present. Higher Capried in thfipfesmce of bit cuttings, a Screen is percentages of silicone may be used if desired but ordilecated abOIlt 2 inches fr m th 5601 t 60 m t0 narilyareunnecessary to produce suitable results. As 1101(1 011ttiIlgS Under Simulated gas drilling condi- -willbe pointed out below, however, the amount of foarnfions with foam, the Cuttings a e moved from the screen ing' agent needed to'remove the oil satisfactorily generaland the cuttiflgsfcan'yiflg P Y foaming agent ly increases with increasing Water content. Systems conunder ifivastigatmn can thus be detelmmedt'ainingin excess of about 40 percent water exhibit con- A preferred method of using this apparatus m testm siderable resistance to removal in this manner. foammg agents involves making P about htef of Silicones of the type contemplated by our invention h oil foamer dissolved i kerosene, crude or the can be employed in clean-out operations carried out in i depending 011 thefiatllrefif p fi testl T316 test the open or uncased portion of an oil Well. In the operaefiected y l'lvltllodrllcmg Inert gas, YP P Y' at-the Tate tionof a well, heavy hydrocarbon residues tend to collect of abo'llt 2 Cublc feet P Emmuteyfor. a Period of about 10 atthe face of the formation and to materially reduce the l The j y of the Tests p' permeability thereof. In circumstances of this sort, we Qfimed ut ate temperature of about 4t) F. The foam employ, for example, a silicone such as an a,w-dichlorop during 2 test Pfiflod discharged Into a phenyl' siloxane, having a viscosity of the order of about reservoir, TESEI'VOITS 0f kIwWn Volume, eXafnlple 1 6-0 cstks., in a concentrationof .35 pound per barrel of Or more liter beakers, and the m volume'estlmateddiesel oil or kerosene. This solution is then injected into After 563mg for ShOTt p i 1116 foam is obsfillved' t0 the well at the rate of about 7 barrels per hour With 1200 bleak and the Volume of hqllld remaining is q q c.f.n1.-of natural gas. This treatment removes the heavy The quefntitf hydrocarbon q 111 this hydrocarbon deposits from the formation face and restores -2 515 an indication the P y the the permeability of the producing zone to a satisfactory Pmlculaf foaming agent mvestlga'tedh level. The kerosene or diesel oil left in the well can be In tests reported lyb mmlbel of 9111- removed by ordinary producing methods or merely by. in- 3 Yi PGIYITIBTS were mvestlgated; The pp used jectting natural gas or an inert gas at a rate of from about W of tha WP Iflfefrfidto immediately above P011111- 400 to about 1 00 cubic feet per minute' mg agent in the concentration listed below was dissolved Similarly, in the case of. a gas well that periodically 1n aboutel hter'of diesel becomes loaded with distillate resulting in decreased gas Table I production, the well can be cleaned out by the use of oil foamers of the type mentioned above. For example, comemm from about 2 to 10 pounds of silicone diluted to 1 pound non of per gallon with a medium boiling range hydrocarbon sol- Compound 332; f gfiffi 552g? f g vent such as kerosene, may be lubricated into the tubing 'cstki Percent, Inches v01" w or siphon string. The silicone can then be forced to the 011 bottom of the well by introducing natural gas and equalizing the. pressure between. the tubing and siphon string. p After the well has been closed in for? to 5 hours, or as tiniii fifigifig dlmethyl 60 1 1 Over 560 long as is required to build up suitable pressure, e.g., B8 28 8-82 ya None 42 0.35 to about .4 p.s.i. per foot of well depth, it can be 59 Dtmetlif lditfiiQiffiII: or 18 None: opened and the flow l-ine directed to a pit or separator to ig g dlethuy'slane Noneget maximum pressure drop and the necessary amount of Methyl triethoxy'silane 0.2 36 None. foaming tobr ing the distillate out of the well. 5381 313911 11 dimethyl silox- 20 0.1 Over 260 In application of our'mvention' to gas dIllllIlg operaane polymer. 1 tions, gas and foamed oil are used as the circulating'fluid. 1g;;n e 3g 1 ;ng; ethy1Sb 5 1' 30 None, The use of gas permits maximum drilling or coring rate, D I 0.1 Over 230 e prevents contamination of the producing zone and cores 8% 8 300 l yet 100 and allows for maximum inflow of formation fillld be- (11 30* 'Nono.' cause of the complete absence of water and very low (nowggr) 24 back pressure on the producing zone. In connection 60 Do 0, 33, Non h ing or gas drilling operations, the silicone in a Gum Tragacanmnnr a g 50 concentration of about .35 pound per barrel of kerosene Higheralkyl y- P y 0.2 48 None. is injected into the input gas. The gas circulation rate fifigffig i g g qfi (L5 12 None. should be sufficient to give an annular velocity of 3000 Ilium chloride 1 feet per minute, and the silicone solution should be injected rapidly enough {0 remove cuttings and give mini 1 Reached collecting line at top of column and came over. mum circulating pressure. The rate at which the silicone 2 Very heavy foam solution is injected into the well should normally be in From the above table, it will be noted that certain the range of 5 to 10 barrels per hour. of the silicon-containing compounds failed completely Oil foaming agents of the type referred to above have to force the diesel oil out of the apparatus in. the form been compared with many different kinds of oil foaming 'of a foam. In every instance, however, in which foammatenals, including other silicon-containing compounds. ing agents of the type covered by the present invention In carryin'g'out these tests, an apparatus was used of the were tested in proper concentration, foam was not only .type described in copendingapplication Serial No. produced from the apparatus, but diesel oil in substantial 733,863, filed May 8, 1958, by James L. Lummus and volumes was obtained duringthe 10-minute test period.

Likewise, it will be observed that prior art oil foaming agents, such as cornstarch, gum tragacanth and nonionic surface active agents were practical failures even when employed in substantial concentrations. The efiect of viscosity, or the degree of polymerization on the efficiency of our novel oil foaming agents is seen by reference to the above table in which the a,w-dimethyl dimethyl siloxane polymer was used. This particular polymer was employed in grades varying in viscosity of from 5 to 100 cstks. It is clear from the information recorded in the above table with respect to such compounds that peak foam formation and oil removal efficiencies are obtained with viscosities lying in the range of from 10 to about 50 cstks.

Table ]1 demonstrates the effect of water and foaming agent concentration on the efficiency of oil removal.

Table II Concentration of YVater, Foaming Wt. Per- Fluid Re- Compounds Agent, cent Based moved,

Wt. Peron Oil Volume cc. cent Based on Oil a,a-diphenyl dimethyl siloxane polymer 10 0.0 462 D 03 (l. 188 10 l. 0 372 10 10. O 385 02 1. 0 112 02 10. 0 0 05 10. 0 98 l0 0. O 406 02 0. 0 167 10. 0 343 O2 10. O 133 In still a third series of tests carried out essentially under circumstances similar to those described above, crude oils from the Midland Farms and Spindletop, Texas, fields were investigated to test the ability of various oil foamers to remove crudes of these types from a simulated well.

1 Samples foamed copiously when diluted with diesel fuel.

In similar tests in which cuttings were introduced into the apparatus and the foaming agent employed in a concentration of .35 pound per barrel of diesel oil, it was found that under simulated well conditions from 60 to 180 pounds of cuttings per hour could be removed from the well using gas rates producing annular velocities of about 3000 feet per minute. With respect to cuttingscarrying capacity, it appeared that polymers having a viscosity of the order of 20 cstks. were superior to those having viscosities of the order of 50 cstks.

The term gas, as used in the present description and claims, is intended to refer to gases which are inert under the conditions of use such as, for example, natural gas or nitrogen, which may be supplied by a conventional inert gas generator. Obviously, air might also be used, so long as combustible mixtures of air and hydrocarbon vapors are avoided. As a practical matter, the avoidance of such mixtures may be difiicult.

We claim:

1. In a process of removing liquid petroleum from a well penetrating a petroleum-containing reservoir by converting said petroleum into a foam, the improvement which comprises incorporating into said petroleum a silicone polymer dissolved in a hydrocarbon solvent selected from the group consisting of diesel oil and kerosene, said polymer having the following general symmetrical structural formula:

wherein X is a member selected from a group consisting of methyl, aryl, alkaryl in which the alkyl group has no more than 2 carbon atoms, and

wherein Y is a halogen atom, and n is a number ranging from about 20 to about 70; and introducing a gas into the resulting solution of said polymer and liquid petroleum at a rate suflicient to form a liquid petroleum foam and to force the latter up and out of said well.

2. The process of claim 1 in which the silicone poly mer has the following general symmetrical structural formula:

in which n is a number ranging from about 20 to about 70. 3. The process of claim 1 in which the silicone polymer has the following general symmetrical structural formula:

(EH3 (3113 (EH: Q CH3 CH3 1) OH;

in which n is a number ranging from about 20 to about 7 O. 4. The process of claim 1 in which the silicone polymer has the following general symmetrical structural formula:

Cl (H13 (H13 $153 Cl @r t- 3 CH3 CH3 1, CH

in which n is a number ranging from about 20 to about 70.

5. The process of claim 1 in which the silicone polymer has the following general symmetrical structural formula:

C z ([3113 3 (3 3 C De MFG CH3 CH3 CH in which n is a number ranging from about 20 to about 70.

6. The process of claim 1 in which said polymer is employed in an amount ranging from about 0.02 to about 5.0 weight percent, based on the liquid petroleum in said well, said polymer having a viscosity of from about 10 to about 60 centistokes.

7. The process of claim 6 in which the water content of the fluids in said well does not exceed about 40 percent, based on the weight of the liquid petroleum.

8. The process of claim 6 in which the water content of the fluids in said well does not exceed about 40 percent, based on the weight of the liquid petroleum, and the silicone polymer employed has the following general symmetrical structural formula:

in which n is a number ranging from about 20 to about 70.

9. The process of claim 6 in which the water content of the fiuids in said well does not exceed about 40 percent, based on the" weight of the liquid petroleum, and the silicone polymer employed has the following general symmetrical structural formula:

in which n is a number ranging from about 20 to about 70.

10. The process of claim 6 in which the water content of the fluids in said well does not exceed about 40 pera cent, based on the weight of the liquid petroleum, and

the silicone polymer employed has the following general symmetrical structural formula:

Cl ClHs (3H3 CIHS Cl CH3 CH3 1: CH3

in which n is a number ranging from about 20 to about 70.

11. In a process for working-over the open hole section of a well penetrating an oil producing zone located in said open-hole section, the improvement which com prises adding to said well a solution of a silicone polymer dissolved in a hydrocarbon solvent selected from the group consisting of diesel oil and kerosene, said polymer 'being present in a concentration of from about .25 to about 15 pounds per barrel of the solvent employed and having the following general symmetrical structural formula:

wherein X is amember selected from a group consisting of methyl, aryl, alkaryl, in which the alkyl group has no more than 2 carbon atoms, and

wherein Y is a halogen atom, and n is a number ranging from about 20 to about 70; and introducing a gas into the liquid contents of the well to form an oil foam, and forcing the latter out of said well.

12. The process of claim 11 in which the silicone polymer is a,wdiphenyl dimethyl siloxane.

13. The process of claim 11 in which the silicone polymer is e o-dimethyl dimethyl siloxane.

14. The process of claim 11 in which the silicone polymer is a,w-dichlorophenyl dimethyl siloxane.

15. In a process of removing liquid petroleum from a well penetrating a petroleum-containing reservoir by con-t verting said petroleum into a foam, the improvement which comprises incorporating into said petroleum, prior to removal thereof from said Well, a silicone polymer dissolved in a hydrocarbon solvent selected from the group consisting of diesel oil and kerosene, said polymer having the following general symmetrical structural formula:

wherein X is a member selected from a group consisting of methyl, aryl, alkaryl in which the alkyl group has no more than 2 carbon atoms, and

wherein X is a member selected from a group consisting of. methyl, aryl, alkaryl in, which thewalkyl group has no more than 2 carbon atoms, and

wherein Y is a halogen atom, and n is a number ranging from about 20 to about 70, whereby said petroleum is converted into a foam, and removing said foam from said surface.

References Cited in the file of this patent UNITED STATES PATENTS Crites et a1 Aug. 1, 1939 Williams et a1 Oct. 21, 1952 OTHER REFERENCES McGregor: Silicones and their Uses, 1954, by McGraw- Hill of New York, page 74. 

1. IN A PROCESS OF REMOVING LIQUID PETROLEUM FROM A WELL PENETRATRING A PETROLEUM-CONTAINING RESERVOIR BY CONVERTING SAID PETROLEUM INTO A FOAM, THE IMPROVEMTN WHICH COMPRISES INCORPORATING INTO SAID PETROLEUM A SILICONE POLYMER DISSOLVED IN A HYDROCARBON SOLVENT SELECTED FROM THE GROUP CONSISTING OF DIESEL OIL AND KEROSENE, SAID POLYMER HAVING THE FOLLOWING GERERAL SYMMETRICAL STRUCTURAL FORMULA: 